The present invention relates in general to methods and apparatus for forming conformable garments having selected discrete elasticized areas on a high speed production basis, and to conformable garments produced thereby; and, more particularly, to forming conformable garments such, for example, as disposable diapers having discrete elasticized areas by stretching a thermoplastic elastomeric material, immobilizing the stretched material in its extended condition, heat treating selected spaced areas of the stretched elastomeric material while in the immobilized extended condition so as to "kill" the elastic properties of the heat treated zones, transferring the immobilized extended material toward a continuously moving web, and affixing the immobilized extended material to the continuous web at production speeds sufficient to produce in excess of 250 diapers per minute while maintaining both the heated non-elasticized zones and the non-heated elasticized zones of the material immobilized with respect to both the transferring means and the continuous moving web. In the preferred form of the invention, the thermoplastic elastomeric material comprises a urethane based material, preferably TUFTANE.RTM., a registered trademark of the manufacturer, B. F. Goodrich General Products Company, Akron, Ohio.
Conventionally, conformable garments having discrete elasticized areas, have been found in a wide variety of ways and utilizing a wide variety of materials. One material commonly employed as the elasticizing element has been natural rubber. Buell U.S. Pat. No. 3,860,003 discloses a disposable diaper formed of such material; while Buell U.S. Pat. No. 4,081,301 describes a process and apparatus for forming such a product. Similarly, Burger U.S. Pat. No. 3,694,815 and Woon et al. U.S. Pat. No. 4,050,462, both assigned to the assignee of the present invention, disclose the use of natural and/or synthetic rubber products to function as an elasticizing element.
Unfortunately, however, natural rubber imposes a number of severe constraints on high speed manufacturing processes. Thus, natural rubber is simply not suitable for storage on support spools because the rubber checks, assumes the shape of the spool, tends to tangle, and binds in the interstices between adjacent underlying loops. Consequently, natural rubber is normally supplied in boxes, with the continuous rubber ribbon being festooned therein. This places a severe limitation on the quantity of material that can be supplied without requiring splicing; and, indeed, at conventional production speeds it is generally necessary to splice such boxes of natural rubber together on the order of every thirty minutes. In addition, since the rubber is festooned in boxes, it tends to tangle and knot as it is removed from the boxes, thereby causing breakage and/or significant amounts of machine down-time. Moreover, natural rubber normally requires talc or other similar lubricants on its surfaces, and such materials seriously interfere with adhesive bonding techniques, thereby necessitating a "detalcing" operation prior to adhesive bonding. Natural rubber is generally rather dark in color and, therefore, when used in garments such as disposable diapers having relatively thin transparent or semi-transparent backing sheets formed of polyethylene or the like, the rubber strips are visible through such material and, therefore, detract from the aesthetic appearance of the product.
It has recently been proposed in published British application No. GB 2 010 682 A, published July 4, 1979, and in published Australian application No. 43750/79, that unvulcanized linear and/or radial block copolymers be utilized as the elasticizing element in conformable garments such as diapers. Such material permits removal of the elastic properties of the block copolymer upon application of heat, ultrasonic, or similar energy inducing means in a manner well known to those skilled in the art.
Over the years, numerous techniques have been developed in the prior art wherein the elastic properties of an elastomeric material are affected by the application of heat. For example, the aforesaid Burger U.S. Pat. No. 3,694,815 assigned to the assignee of the present invention contemplates freezing of an elastic material while the material is in its stretched or extended state so as to immobilize the material while it is being applied to a garment; and, thereafter, thawing the frozen material to restore its elasticity. In Freres et al. British Pat. No. 783,726, the patentee coats a stretched elastic material with a semi-rigid dressing to immobilize the stretched elastic and, thereafter, applied heat to melt the dressing and restore the elastic properties.
Mason U.S. Pat. No. 3,245,407, Althouse U.S. Pat. No. 3,639,917, and Koch U.S. Pat. No. 3,912,565 describe various products and methods wherein selected materials are fastened into a garment and subsequently heated in selected areas thereof while in a contracted or non-stretched condition so as to cause the heated areas to become shirred or elastic in nature--i.e., a heat shrink process used to impart elasticity to selected areas of the garment.
However, despite all of the efforts that have been made to provide a facile, economical process for mass production of conformable garments such, for example, as disposable diapers, problems have, prior to the advent of the present invention, continued to plague the industry. In addition to many of the problems described above with regard to natural rubber--viz., difficulties in feeding continuous runs thereof without tangling, knotting and/or breakage, difficulties in adhesive bonding as a result of surface lubricants, tension uniformity, etc.--many of the thermoplastic elastomeric materials that have been suggested present similar, as well as somewhat different problems. For example, since the elastic material is here contemplated for usage in garments, it is important that the material be characterized by its strength; not only strength in usage, but also in the high speed manufacturing processes employed. Where the material is to be heat treated to "kill" the elastic properties thereof in selected discrete areas, it is important that the heated material possess sufficient strength as to resist breakage, particularly when the heated material is being worked on in a high speed continuous production process. Color characteristics and adhesive bonding properties have continued to present problems.